Added test test_list_thing_groups()
Added test test_list_thing_groups()

william-richard/moto,william-richard/moto,spulec/moto,spulec/moto,spulec/moto,william-richard/moto,william-richard/moto,spulec/moto,william-richard/moto,spulec/moto,spulec/moto,william-richard/moto